This 3 stars is really 3.5, and is more personal reaction than attempt at an objective rating. This is a good book. And I liked the first half of it, in which our narrator, Esther, is doing a fancy internship in New York City. She feels lost, she's not sure what she wants to do with her life, she worries that the only thing she's good at is winning scholarships and prizes. I can relate to that and I think a lot of women can (and men too - but I read somewhere that women have a harder time making a successful transition from being good at school to doing well in the workplace). It is also interesting just reading about life in what's presumably the 1950s; things have changed a lot while staying remarkably the same in some unexpected ways.
However, the second half the book, when Esther suddenly loses touch with reality, mostly lost me. I didn't understand it. Perhaps that's more my failing than Plath's, which is why I warned you this is a personal response. But it didn't make much sense to me, and in the end the book left me a bit cold.